Electrophotographic machines, such as, for example, copiers and printers, produce images by forming a latent image charge pattern on a dielectric member. The dielectric member carries the latent image through a developing station wherein pigmented toner particles are drawn by electrostatic attraction onto the latent image charge pattern. An electric field is applied to transfer the image from the dielectric member onto either an intermediate transfer member and then to an image substrate, such as, for example, a piece of paper, or directly from the dielectric member onto the image substrate.
The image substrate is then separated from the dielectric member or intermediate transfer member and transported to a fixing station wherein the image is fixed, such as, for example, by fusing, to the image substrate. The fixing station generally includes one or more heated fusing rollers and one or more opposing pressure rollers which are rotated to pass the image substrate through a nip formed between the rollers. Under the heat and pressure within the nip, the toner particles are fused to the image substrate. The image substrate is then separated from the fusing and/or pressure rollers.
In some electrophotographic machines, particularly machines capable of producing multi-color images, the image substrate carrying the fused image may then be carried to a glossing station wherein the surface finish and/or image gloss are enhanced or manipulated by a glossing process. Generally, the glossing process includes a glossing or finishing belt carrying the image substrate through a nip formed between a heated “glossing roller” and an opposing pressure roller. As will be understood by one of ordinary skill in the art, the term “glossing roller” is not used to indicate that the glossing roller itself provides gloss or finish to the image substrate, but rather is used to indicate the roller is part of or located within the glossing station.
The image carrying substrate and the belt are cooled after the nip and before a release roller in order to prevent offset of the toner or marking particles from the image substrate to the finishing belt. The finishing belt carrying the image substrate typically has a surface with a very smooth and shiny coating that produces image substrates with a similar smooth and shiny surface. Alternatively, the finishing belt carrying the image substrate may have a surface with a textured coating that produces image substrates having a similarly textured surface. The glossing station may be onboard or integral with a particular electrophotographic machine or it may be an off-board accessory.
Release fluid (typically silicon oil) may be applied to the fusing and/or pressure rollers of the fixing station in order to facilitate release of the image substrate from and in order to ensure toner does not adhere to the rollers. The release oil, however, occasionally spreads onto an image substrate and contaminates the image thereon. When the image substrate is processed through the glossing station, release fluid on the image may result in undesirable image artifacts, such as, for example, haze, ghosting, rivers. The release fluid may also cause ripples or wrinkles in the image substrate due to reduced friction in the glossing nip.
Therefore, what is needed in the art is an electrophotographic machine that reduces the likelihood of undesirable image artifacts caused by glossing of an image contaminated with release oil.
Furthermore, what is needed in the art is a process for reducing undesirable image artifacts caused by glossing of an image contaminated with release oil.